In this work, the ratcheting-behavior of 9%Cr-1%Mo ferritic-martensitic steel is studied with uniaxial cyclic loading. To describe the ratcheting-behavior of this steel, a visco-plastic constitutive model with consideration of cyclic softening of Reduced Activation Ferritic Martensitic steels is further modified, based on the analysis of back stress. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.